Allylation reaction of carbonyl compounds

Si. rra(pentafluorophenyl)boron was found to be an efficient, air-stable, and water-tolerant Lewis-acid catalyst for the allylation reaction of allylsilanes with aldehydes.167 Sc(OTf)3-catalyzed allylations of hydrates of a-keto aldehydes, glyoxylates and activated aromatic aldehydes with allyltrimethylsilane in H2O-CH3CN were examined. a-Keto and a-ester homoallylic alcohols and aromatic homoallylic alcohols were obtained in good to excellent yields.168 Allylation reactions of carbonyl compounds such as aldehydes and reactive ketones using allyltrimethoxysilane in aqueous media proceeded smoothly in the presence of 5 mol% of a CdF2-terpyridine complex (Eq. 8.71).169... 

This chapter has introduced the aldol and related allylation reactions of carbonyl compounds, the allylation of imine compounds, and Mannich-type reactions. Double asymmetric synthesis creates two chiral centers in one step and is regarded as one of the most efficient synthetic strategies in organic synthesis. The aldol and related reactions discussed in this chapter are very important reactions in organic synthesis because the reaction products constitute the backbone of many important antibiotics, anticancer drugs, and other bioactive molecules. Indeed, study of the aldol reaction is still actively pursued in order to improve reaction conditions, enhance stereoselectivity, and widen the scope of applicability of this type of reaction. 

T. Akiyama, J. Iwai, Scandium Trifluoromethane-sulfonate-Catalyzed Chemoselective Allylation Reactions of Carbonyl Compounds with Tetraallylgermane in Aqueous Media Tetrahedron Lett. 1997,38, 853-856. 

A partially soluble polyallylscandium triflamide ditriflate 45 was prepared and used to catalyze a three-component coupling reaction.67 An aldehyde, an aromatic amine, and an alkene were mixed in the presence of the catalyst to afford tetrahydroquinolines (equation 17). The catalyst was recovered from the reaction mixtures by precipitation with hexane and could be recycled without loss of activity. Another polymer-supported scandium catalyst was prepared by treating Nafion with scandium chloride to afford the Nafion-scandium catalyst 46.68 This catalyst was used in allylation reactions of carbonyl compounds by tetraallyltin (equation 18). It could be easily recovered by filtration and reused without appreciable loss of activity. 

The allylation reaction of carbonyl compounds is a classical but excellent method for constructing highly functionalized organic molecules. More recently, allylation... 

The control of diastereoselectivity in the allylation reaction of carbonyl compounds with allylic indium reagents has been an important issue since the discovery of the indium-mediated carbonyl allylation. As earlier discussions have been summarized in the precedent reviews,6-24 only relatively recent references are cited below. 

Sc(OTf)3 promoted allylation reactions of carbonyl compounds were reported, (a) Tetraallylger-manium T. Akiyama, J. Iwai, Tetrahedron Lett. 1997, 38, 853-856. (b) Allyltrimethylsilane V. K. Aggarwal, G. P. Vennall, Tetrahedron Lett. 1996,37, 3745-3746. Sc(OTf)3 is also an effective catalyst for the allylation of imines with allyltributyltin. (c) C. Bellucci, P. G. Cozzi, A. Umani-Ronchi, Tetrahedron Lett. 1995,36,7289-1292. 

The allylation reactions of carbonyl compounds catalyzed by chiral Lewis acids represent a powerful new direction in allylmetal chemistry. Yamamoto and coworkers reported the first example of the catalytic enantioselective allylation reaction in 1991, using the chiral (acyloxy)borane (CAB) catalyst system (see below) [288]. Since then, several additional reports of the catalytic allylation reaction have appeared. To date, the most effective catalyst systems reported for the enantioselective reaction of aldehydes and Type II allyl- and crotylstannane and silane reagents include the Yamamoto CAB catalyst and catalysts complexes composed of various Lewis acidic metals and either the BINOL or BINAP chiral ligands [289-293]. Marshall and Cozzi have recently reviewed progress in the enantioselective catalytic allylation reaction [294, 295]. 

Table 14-11. Sc(OTf)3-Catalyzed allylation reactions of carbonyl compounds with tctraallyltin.

Lewis acid-promoted allylation reactions of carbonyl compounds with allyltrialkyltin were reported, (a) Yamamoto, Y Yatagai, H. Naruta, Y Maruyama, K. J. Am. Chem. Soc. 1980, 102, 7107. (b) Pereyre, M. Quintard, J.-R Rahm, A. Tin in Organic Synthesis, Butterworths, London, 1987, p 216. 

Allylation Reactions. The allylation reactions of carbonyl compounds with tetraallyltin proceed smoothly under the influence of a catalytic amount of Sc(OTf)3. The reaction can be carried out in aqueous media as exemplified by unprotected sugars that react directly to give the adducts in high 3deld (eq 11). ... 

In an original approach, reactive metallic powders of copper, cobalt, and zinc have been generated by pulsed sonoelectrochemical reduction. Zinc produced in this manner effects allylation reactions of carbonyl compounds (p. 223) in higher yields than commercial powders... 

In allylation reactions of carbonyl compounds in water, the reaction is greatly accelerated in the presence of both Sc(DS)3 and HCl (Scheme 3.61). ... 

Hachiya, 1. and Kobayashi, S., Aqueous reactions with a Lewis acid and an organometalhc reagent. The scandium trifluoromethanesulfonate-catalyzed allylation reaction of carbonyl compounds with tetraallyltin, /. Org. Chem., 1993, 58, 6958-6960. 

Lanthanum triflate immobilized onto the mesoporous SBA support [105] affords the allylation reactions of carbonyl compounds with tetraallytin, which are among the most fundamental and important C-C bond-forming reaction (Equation (8.44)) [135]. 

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